1. Field of the Invention
This invention relates, generally, to a dental articulator, and in particular, to an articulator having new and improved mechanisms for handling the plaster of paris or other molding material, and also relates to a new and improved anterior post which provides a clear visibility of the anterior teeth and the enhanced capability for working on the anterior teeth.
2. Description of the Background
The articulator disclosed herein is useful in all types of restoration work, but has been particularly designed for crown and bridge work. Tooth restoration work in dentistry is presently more or less divided between dentures that are removable from the mouth for cleaning and tooth restorations that are generally fixed to the teeth. These latter are known as crowns and fixed bridges.
When a dentist desires to prepare crowns or fixed bridges, he prepares the natural tooth by grinding to a suitable form to allow for sufficient bulk of metal or porcelain when the metal or porcelain is fabricated into crown and cemented into place over the prepared natural tooth. The dentist then takes an impression of that part of the mouth in which he has been working and then an impression of the teeth opposite that part of the mouth in which he has been working. The dentist then takes a wax bite of the entire area involved. The wax bite uses a material composed of two thin pieces of flat wax of approximately fourteen gauge in thickness with a sheet of tin foil or cellophane between the sheets. This bite is placed between the occluding surfaces of the teeth, and the patient then bites down into the wax to register the relationship between the upper and the lower jaw.
These impressions of the mouth are then used as molds and are filled with a material commonly referred to as dental stone because of its extreme hardness. When the stone has set up sufficiently hard, it is removed from the molds or impressions of the mouth, and the dentist then has a more or less perfect reproduction of the various teeth of the area in which he is working, including the grounddown tooth which is to be fitted with a crown or fixed bridge. The wax bite is then placed between the teeth formed of the dental stone to obtain the registry of the upper and lower jaws with each other. This combination of upper and lower jaws with the wax bite between them is then mounted on an articulator by covering the surfaces of both upper and lower jaw and by covering the surfaces of the lower member of the articulator and the upper member of the articulator with plastic of paris or similar material, which sets up all the upper and lower jaw impressions in perfect registry. The wax bite is then removed, and the casts of the teeth are now ready for building the desired kind of restoration in the conventional manner.
The gold or porcelain crown is then prepared in the usual fashion (usually by the lost wax method), and when completed it is then mounted on the cast of the prepared tooth or teeth, and the dentist or technician then checks the gold or porcelain crown for a proper fit. The human jaw has various normal motions, one of which is a forward and backward movement of the jaws relative to each other. The newly prepared crown must then be checked for such movement. Also, one of the normal movements of the human jaw is lateral or sideways movement of the teeth with respect to each other, and the dentist or technician must then next check the gold or porcelain crown for a proper clearance and freedom from obstruction by this lateral movement.
Typical of the prior art in this area is that of U.S. Pat. Nos. 1,319,737 to Wadsworth; 1,471,019 to Wilson: 2,697,279 to Clawson; and 4,175,325 to Beckwith.
It is known, for example, in U.S. Pat. No. 4,175,325 to Beckwith, to place the plaster of paris directly on the lower bow of the articulator. However, the plaster of paris will then harden on the articulator and become very difficult to clean up. Moreover, with no means for retaining the plaster of paris, it will tend to slump and fall off on the surrounding surfaces and in general be very messy.
Those in the art have also used an adjustable anterior post which will provide for the optimum vertical distance between the upper and lower sets of teeth. However, the prior art anterior posts have provided an obstruction to working on the anterior teeth.
It is therefore the primary object of the present invention to provide a new and improved articulator which allows the models to be more easily removed from the articulator.
It is another object of the present invention to provide a new and improved means in a dental articulator for maintaining the optimum vertical distance between the upper and lower teeth being manipulated.
It is yet another object of the present invention to provide a new and improved anterior post for use with a dental articulator for improving the visual access to the front teeth.
It is still another object of the present invention to provide a new and improved model holder for use with a dental articulator.